In particular, if \(S\)  separates \(A\)  and \(B\) , then \(A\cap B\subseteq S\) . Furthermore, given a set \(W\)  of vertices, we say that a set \(S\)  of
vertices is a balanced separator of \(W\)  if \(|W\cap C|\le |W|/2\) 
for every connected component \(C\)  of \(G\setminus S\) . A \(k\) -separator
is a separator \(S\)  with \(|S|=k\) . The treewidth of a graph is closely
connected with the existence of balanced separators:
[[1]}, [2]}]
